Known control membranes of this kind are made of a material which is soft so as to be bendable and this material includes a fabric having a rubber coating. A reinforcement plate is provided in the center region of the membrane and is disposed on a first side of the membrane which faces into the carburetor chamber. The reinforcement plate is attached to the membrane by means of a rivet and a plain washer disposed on the second side of the membrane. A controller lever lies against the reinforcement plate riveted to the membrane and displaces a nozzle needle of a nozzle for controlling the fuel. The controller lever can be pressed by means of the force of a spring in a direction against the reinforcement plate.
A pressure difference to the ambient pressure is generated because of the underpressure developed in the carburetor chamber with a pressure force being developed by the membrane which is transmitted via the reinforcement plate to the controller lever which is movable against the force of the spring. The flow of fuel is then controlled by means of this pressure difference. Without the reinforcement plate, the controller lever would press into the membrane and would experience only a slight pressure force.
Carburetor controller membranes of this kind made of fabric-reinforced rubber having a reinforcement plate riveted thereto are not sufficiently resistant to corrosive fuels so that the rubber coating separates from the fabric in the presence of, for example, lead-free fuels or various alcohol additives. In addition, such membranes have only a limited temperature range in which they can be utilized.
A further significant disadvantage is that the riveted reinforcement plate can wobble because of vibrations so that the plate no longer coacts with the membrane and more or less separates from the membrane surface. This condition can lead to leaks at the rivet connections through which the fuel can escape. The formation of leaks at the rivets can be facilitated because of the local deformation of the membrane at the riveted connection.
Furthermore, the reinforcement plate can lift in response to pressure shocks so that a delayed response of the controller lever can occur. Also, the manufacture of the known carburetor control membranes is complex since the membrane, the rivet, the reinforcement plate and the plain washer comprise, at least in part, very different materials which each require their own processing steps and which finally must be assembled with each other.